This invention relates to one way clutch mechanism for bicycle freewheel hubs, and more particularly to such a type of one way clutch mechanism that includes a pair of conical clutch faces arranged for engagement and disengagement with each other.
A typical model of the conventional one way clutch mechanism of the above type is disclosed for example in U.S. Pat. No. 3,709,341 to Schulz, wherein one conical clutch face is formed on a clutch member (coupling member) which is mounted on a driver by threads so as to move axially outwardly when the driver is rotated in a forward direction, while the other conical clutch face is formed on a hub shell, so that the driver transmits torque to the hub shell when the clutch faces are in engagement but permits free rotation of the hub shell when the clutch faces are in disengagement.
In the above conventional mechanism, the engagement between the pair of clutch faces are realized by frictional resistance and no positive and reliable means is provided for restricting undesirable relative slippage therebetween. Accordingly, for the purpose of effective torque transmission by minimizing the slippage, the tapering angles of the conical clutch faces are generally of smaller than 30.degree. so that frictionally contact area therebetween can be increased. Further, a spring is provided in order to urge the clutch member axially outwardly to improve reliability of the operative engagement between the clutch faces.
As will be apparent from the above description, the conventional mechanism appears advantageous from the viewpoint of effective torque transmission. However, it has such a disadvantage that a quick and easy disengagement between the clutch faces is sometimes difficult to obtain because of their relatively large contact area and small tapering angles in addition to the function of the spring so arranged as to always urge the clutch member axially outwardly to force the conical clutch face of the driver against the mating clutch face of the hub shell. If disengagement between the clutch faces cannot be attained instantly, pedals continue its rotation regardless of the fact that a cyclist has stopped his pedalling operation.
It is, therefore, an object of the invention to substantially reduce the above-discussed disadvantages observed in the conventional one way clutch mechanism for bicycle freewheels.
Another object of the invention is to provide an improved one way clutch mechanism for bicycle freewheel hubs, which permits easy and quick disengagement between conical clutch faces.
A further object of the invention is to provide an improved one way clutch mechanism for bicycle freewheel hubs, which permits reliable, non-slipping engagement between conical clutch faces.
Other objects, features and advantages of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become obvious to those skilled in the art from this detailed description.
According to the present invention, there is provided one way clutch mechanism for bicycle freewheel hubs which comprises a driver having one or more sprockets thereon and relatively rotatable with respect to a stationary axle, a hub shell relatively rotatable with respect to the axle, a toothed, inward conical clutch face formed internally of the hub shell, an internally threaded clutch member relatively rotatably mounted on a threaded section of the driver so as to axially move back and forth within a limited range and having an outward conical clutch face with claws formed therewith, and a coil spring so arranged as to urge the clutch member not axially outwardly but axially inwardly so as to force the outward clutch face away from the inward clutch face, wherein the tapering angles of the inward and the outward clutch faces may be greater than 30.degree. for better disengagement from each other and reliable engagement between the clutch faces are attained not by friction but by teeth-claws engagement. The clutch mechanism of the invention can be utilized as a known ratchet mechanism conventionally incorporated in a bicycle freewheel hub with such an advantage that the known tinkling noises can be substantially eliminated. The clutch mechanism of the invention can also be utilized as that for a freewheel hub with coaster brake.